Up to 30 percent of the vertebrate eye lens is composed of the small heat shock protein alpha-crystallin. This protein acts as a molecular chaperone, preventing the stress-induced aggregation of denatured proteins that can lead to cataracts. The central premise of this proposal is that the chaperone activity of alpha-crystallin is dependent on temperature, and that its amino acid composition has evolved to maintain chaperone function in different thermal environments. Alpha-crystallin consists of two subunits, alphaA and alphaB, that arose from a gene duplication event and have different chaperone properties. This proposal seeks to determine the relationship between the structure and chaperone function of alphaA- and alphaB-crystallin from the zebrafish. This study will assay, for the first time, chaperone function of alpha-crystallin from an ectothermic vertebrate. This information will be directly compared to the structural and chaperone properties of human alphaAand alphaB-crystallin to determine whether chaperone function adapts to the physiological temperatures of different species. These data will provide a reference point for a large body of researchers interested in small heat shock protein function and cataracts, and will build the basic knowledge necessary for further studies on the thermal adaptation of alpha-crystallin. The aims proposed will be accomplished using an interdisciplinary approach combining molecular biology, protein biochemistry, ecology and evolution. The senior investigator's diverse background in fish evolution, fish ecology, and molecular techniques makes him uniquely qualified to carry out this interdisciplinary research project.